To better control the pollution caused by power plants, the Government will specify the total emission cap in their licences upon renewal, Secretary for Environment, Transport & Works Dr Sarah Liao says.

To meet the specified emission caps, the power plants may implement such measures as raising the share of natural gas in power generation, purchasing higher quality coal and retrofitting their coal-fired generation units with desulphurisation and nitrogen oxide removal systems, she said

Dr Liao told lawmakers today the Government is processing the application for Castle Peak Power Station's licence renewal. The total emission cap will take effect on renewal.

Similarly, when the licence of another coal-fired power plant - Lamma Power Station - expires in September 2006, the Government will specify the total emission cap in the new licence, she added.

Sulphur content capped at 1%

Coal supplied in the international market may have a sulphur content as high as 4% or more, Dr Liao said, depending on the sources. Coal with sulphur content below 1% is considered as low-sulphur coal, and has a small impact on the environment.

Low-sulphur coal is used in local electricity generation since the Environmental Protection Department issues licences to power plants under the Air Pollution Control Ordinance. It stipulates that the coal used for power generation may not exceed 1% in terms of sulphur content, she said.

Since the sulphur content of coal varies according to sources and batches, the annual average sulphur content of coal used for power generation in Hong Kong will also vary, normally within the range of 0.4% to 0.7%.

Although the sulphur content of coal used by one power company last year was relatively higher than in the previous year, the annual average sulphur content did not exceed 0.5%, indicating the coal used was still of reasonably high quality.

Dr Liao said the percentages of electricity generated by local power plants using low-sulphur coal and natural gas were 81% and 19% in 2003, 74% and 26% in 2004, and 69% and 31% in 2005. Oil was also used, but it accounted for less than 1% of the power generated.

Besides respirable suspended particulates, she said other pollutants such as sulphur dioxide, nitrogen oxide and volatile organic compounds may also affect visibility by forming particulates through photochemical reactions.

According to the 2002 Hong Kong-Guangdong Joint Study on Air Quality in the Pearl River Delta Region, the total emissions of respirable suspended particulates, sulphur dioxide, nitrogen oxide and volatile organic compounds from the region and Hong Kong amounted to 257 kilotonnes, 596 kilotonnes, 565 kilotonnes and 465 kilotonnes respectively in the base year of 1997.

Of these four major pollutants, Hong Kong contributed to 5%, 13%, 20% and 12% respectively of the total emissions, with the Pearl River Delta region making up the rest.

Dr Liao said at present, the Environmental Protection Department and Guangdong authorities are working in collaboration on the 2003 PRD Regional Emissions Inventory, which will identify changes in air pollutants emitted from the two places since 1997. The Inventory is expected to be completed by the end of this year.